1. The Field of the Invention
The present invention pertains to a water diffusion plate used to induce layered fluid flow for the purpose of decreasing the effects of water slugging upon injections of large quantities of cold water into active steam lines during steam generator equipment cold start-up.
2. The Prior Art
A problem associated with the start-up of steam generating equipment has to do with cold water condensate left in the system from previous operations. All parts of the steam generating system do not simultaneously reach operating temperatures so there is the possibility that slugs of this cold water could be driven into hot steam headers. This results in a violent reaction between the steam and water.
This reaction has been known to cause structural damage in some steam header systems ranging from bending or shearing 1" thick steel bolts to cracking of concrete foundations at critical guide supports. This damage is a safety concern since, when the system is started, there generally are personnel in the immediate vicinity of the headers and they could be injured as a consequence of the damage. Repairs of the facilities to restore them to a safe operating level can be as high as $40,000 per header.
An example of the use of a steam generator where this would be a problem is the field of secondary petroleum recovery. Steam is pumped into a formation to heat the in situ oil to both change the viscosity and density of the oil and drive it away from steam injection wells toward production wells. Injection of steam can also serve to increase the pressure within a formation to drive the oil. Upon start-up of the steam operation, a separate injection system could be used to inject cold water down a start-up well with the water flow being diverted into the steam header after the water attains a similar temperature and pressure with the steam flow in those lines. But this is a costly process in terms of hardware required plus either an operator or automation to monitor and switch the flow.
It is known that, when the temperature differential between water and steam is too diverse, intermixing multiphase flow can result in a reaction having violent effects on the associated piping system. This reaction is largely due to condensation shock and is particularly apt to occur when large slugs of water, originating from a cold portion of the system, are driven into a steam header, which has reached operating temperatures. Thus there is a potentially dangerous situation existing for a period of time after steam generator start-up.